1. Technical Field
The present disclosure relates to a sewing machine comprising a sewing mechanism including a needlebar with a lower end to which a sewing needle is attached, a needle thread take-up and a thread seizing hook, and a cloth pressing mechanism including a presser foot pressing workpiece cloth, the sewing machine being capable of free-motion sewing while the workpiece cloth being manually fed.
2. Description of the Related Art
Conventional household sewing machines can carry out a normal sewing in which a feed dog mounted on a sewing bed is moved back and forth so that sewing is carried out while the workpiece cloth is fed. In addition to the normal sewing, the household sewing machines are constructed and arranged so as to be capable of free-motion quilting in which the feed dog is retracted inside the bed and sewing is carried out which an operator manually moves workpiece cloth freely. When quilting is to be carried out in a free-motion manner, a presser bar to which a presser foot is attached is moved upward so that the presser foot is held at a position spaced away from workpiece cloth by a predetermined short distance, whereby the workpiece cloth placed on the upper surface of the bed is manually movable freely.
For example, JP-A-2002-292175 discloses a sewing machine including a sewing arm provided with a needlebar with a lower end to which a sewing needle is attached, a needlebar driving mechanism vertically driving the needlebar, an image sensor loading, as a still image, a part of image taken from workpiece cloth, and the like. Thus constructed sewing machine is arranged so that a microcomputer measures at intervals of predetermined time a distance by which the workpiece cloth is fed and so that an operating speed of the needlebar is changed according to the measured distance. More specifically, the vertical movement of the needlebar is slowed down when the distance by which the workpiece cloth is fed is short, whereas the vertical movement of the needlebar is speeded up. As a result, stitches are formed at a set pitch even when workpiece cloth is fed by manual operation.
In the above-described sewing machine, however, the vertical movement speed of the needlebar, that is, when stitches are formed while the operator manually moves the workpiece cloth a rotational speed of a sewing machine motor is rapidly changed according to the distance by which the workpiece cloth is fed. Consequently, a beginner unfamiliar with sewing is forced to carry out quilting by feeding the workpiece cloth while having anxiety. Thus, there is a problem that the operator cannot sufficiently enjoy quilting.